Physics Stack Exchange
Physics Stack Exchange

Questions tagged [models]

DO NOT USE THIS TAG just because the involved physics is based on a model. All physics descriptions are inherently model-based. This tag is reserved specifically for addressing model development, validity, simplification, or other meta-model questions.

DO NOT USE THIS TAG just because the involved physics is based on a model. All physics descriptions are inherently model-based, so this tag is not useful for questions about applying or understanding a specific model. Rather, this tag is reserved specifically for addressing model development, validity, simplification, other meta-model questions, or the nature of models within physics.

406 questions
217
votes
16 answers

Why don't electrons crash into the nuclei they "orbit"?

I'm having trouble understanding the simple "planetary" model of the atom that I'm being taught in my basic chemistry course. In particular, I can't see how a negatively charged electron can stay in "orbit" around a positively charged nucleus.…
orome
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150
votes
7 answers

Why do people categorically dismiss some simple quantum models?

Deterministic models. Clarification of the question: The problem with these blogs is that people are inclined to start yelling at each other. (I admit, I got infected and it's difficult not to raise one's electronic voice.) I want to ask my question…
G. 't Hooft
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91
votes
11 answers

Why must a physical theory be mathematically self-consistent?

I always read in modern physics textbooks and articles about the need for physical theories to be mathematically self-consistent, which implies that the theories must not produce contradictions or anomalies. For example, string theorists are proud…
Maxis Jaisi
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41
votes
12 answers

What does it mean when people say "Physics break down"?

So I keep hearing people talking about how physics break down at for example the center of a black hole. And maybe I am just to stupid but, why? How can we say that? For all we know a black hole could just be a very dense sphere. Kind of like a…
Erik Hall
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40
votes
4 answers

Why can't the Navier Stokes equations be derived from first principle physics?

At the 109th UCLA Faculty Research lecture, Seth Putterman gave a talk on Sonoluminescence. During the lecture he emphasized that "The Navier Stokes equations cannot be derived from first principles [of physics]". In physics there are lots of first…
docscience
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37
votes
4 answers

Floating a ping pong ball in the air just using a pen!

Caution: Apparently this problem is harder than it seems! There is a well known phenomena, which I first learnt about when I was a 10 years old kid. You can levitate a ping pong(or whatever not-so-heavy) ball in the air by blowing throw an empty…
Ali
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37
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3 answers

Why can't many models be solved exactly?

I have been told that few models in statistical mechanics can be solved exactly. In general, is this because the solutions are too difficult to obtain, or is our mathematics not sufficiently advanced and we don't know how to solve many of those…
Daphne
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36
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11 answers

Can mathematics lead to a result which is physically untenable?

Consider some known physical fact, e.g. $\nabla \cdot \mathbf B = 0$ for the magnetic induction $\mathbf B$. Now, is it possible that a mathematical theorem exists, which yields a wrong prediction? E.g. a hypothetical - correctly proven - theorem…
Javi
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35
votes
7 answers

How seriously can we take the success of the Standard Model when it has so many input parameters?

The Standard Model of particle physics is immensely successful. However, it has many experimentally fitted input parameters (e.g. the fermion masses, mixing angles, etc). How seriously can we take the success of the Standard Model when it has so…
Solidification
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32
votes
9 answers

Does amplitude really go to infinity in resonance?

I was recapping the forced oscillations, and something troubled me. The equation concerning forced oscillation is: $$ x=\frac{F_0}{m(\omega_0^2-\omega^2)}\cos(\omega t) $$ I don't understand why this equation predicts that the amplitude will…
Efe Zaladin
  • 687
28
votes
6 answers

General relativity (and other theories) when proven wrong

So, I have been watching some science videos regarding Einstein's theory on general relativity and until today the predictions based on his equations have been proven to stand. My question would be: what happens in the scientific community if one…
complex
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28
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6 answers

Why exactly are singularities avoided or "deleted" in physics?

What is the real reason that make us reject singularities everytime we see them in a theory/model? For example, in GR, it is predicted that black holes singularities have infinite density. This makes GR useless to predict the behaviour of the…
Oni Ein
  • 415
26
votes
5 answers

What does it mean that physics no longer uses mechanical models to describe phenomena?

I've just started reading Sommerfeld's Lecture on Mechanics, with no background in physics (only in math). Can you explain to me what the author means with the bold sentence? Mechanics is the backbone of mathematical physics. Though it is true …
Jhdoe
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25
votes
9 answers

How does a particle know how to behave?

How does a particle know it should behave in such and such manner? As a person, I can set mass is so and so, charge is so and so - then set up equation to solve its equation of motion but who computes that equation of motion for a particle in real…
Young Ha Kim
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24
votes
3 answers

What does it mean for a law to be fundamental?

I was recently reading up about Coulomb's law and Gauss law and several sources seemed to state that the Gauss law was more "fundamental" than Coulomb's law even though one is deducible from the other, which got me thinking: what does it even mean…
Ritik Garg
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